L.B.
I dont know what school district you are in - but both my kids were in GT in Cy-Fair ISD from kindergarten all thru 12th grade. they were both in Scouts (my son earned his Eagle and my daughter her Gold Award) and both were in high school marching band. My son made a 1300 out of 1600 on his SAT and my daughter a 1200 out of 1600 on her SAT.
i found the following to be true: The students in the GT classes enjoy "being there" and pay much better attention to the teachers - thus more teaching gets accomplished and actually more classwork gets completed. My kids never really had all that much homework because they were able to finish it in class.
My rule was always do your homework as soon as you get home - before you go out to other activities. Thus, we never had that problem of worrying about getting it done.
So - if your child wants to be in the GT classes - I say definately do it.